Place Value Math Riddles — Grades K–8

5 riddles per grade level. Click Show answer to reveal the solution and explanation.

Middle School (6–8) · Scientific Notation

Riddle 1 of 5

I am written in scientific notation as 3.7 × 10⁴. The exponent 4 means I multiply 3.7 by 10,000 — which shifts my decimal point 4 places to the right. What is my standard form?

Answer: 37,000 3.7 × 10,000 = 37,000. Decimal shifts 4 places right: 3.7000 → 37000

Riddle 2 of 5

The tiny number 0.000056 wants to dress up in scientific notation. The coefficient must be between 1 and 10. The decimal moves 5 places right to get to 5.6. What is the missing coefficient in ___ × 10⁻⁵?

Answer: 5.6 0.000056 = 5.6 × 10⁻⁵. Moving decimal 5 right gives 5.6, so exponent is –5.

Riddle 3 of 5

I am the PRODUCT of 4 × 10³ and 2 × 10². Multiply the coefficients (4 × 2) and ADD the exponents (3 + 2) to find me in scientific notation. What am I?

Answer: 8 × 10⁵ 4 × 2 = 8, and 10³ × 10² = 10⁽³⁺²⁾ = 10⁵. So the answer is 8 × 10⁵ = 800,000

Riddle 4 of 5

I am written in scientific notation as 2.5 × 10⁻³. The negative exponent means I am VERY small — it moves my decimal 3 places to the LEFT. What is my standard (decimal) form?

Answer: 0.0025 2.5 × 10⁻³ = 2.5 ÷ 1,000 = 0.0025. Decimal moves 3 places left.

Riddle 5 of 5

My coefficient is 1.5. My exponent on the power of 10 makes me equal exactly 1,500. Since 1.5 × ? = 1,500, and 1,500 ÷ 1.5 = 1,000 = 10³, what power of 10 am I multiplied by?

Answer: 10³ (so 1.5 × 10³) 1.5 × 10³ = 1.5 × 1,000 = 1,500 ✓. The exponent is 3.